Cooler, electronic apparatus, and method for fabricating cooler

ABSTRACT

This invention provides a cooler having an excellent cooling performance, which is capable of being downsized and low-profiled, an electronic apparatus and a method for fabricating the cooler. The cooler ( 1 ) comprises lower board member ( 10 ) and upper complex board members. The lower board member ( 10 ) is made from plastic material and has a cavity portion ( 11 ) for allowing water or vapor to be circulated therein. The upper complex board members comprise board member ( 20 ) for a condenser part, upper board member ( 30 ), and board member ( 40 ) for a wick part. The board members ( 20 ) and ( 40 ) for the condenser part and the wick part, respectively, are made from metallic material having higher thermal conductivity such as copper and nickel. Each of the members has a groove for allowing them to be served as the condenser and the wick. The upper board member ( 30 ) includes an opening ( 32 ) or ( 34 ) for allowing the board member ( 20 ) or ( 40 ) for the condenser part or the wick part to be incorporated, and a hollow ( 31 ) for heat insulation.

TECHNICAL FIELD

The present invention relates to a cooler for transferring heatgenerated from a driver for card-typed storage medium as a component ina personal computer, a digital camera, and the like, to cool the storagemedium, and a method for fabricating the cooler. The present inventionalso relates to an electronic apparatus such as a personal computer, anda digital camera, which is equipped with the cooler.

BACKGROUND ART

Since a compact and low-profile storage medium such as a memory stick(registered trademark), smart media (registered trademark), and acompact flash (registered trademark) as compared with conventional onesuch as a floppy (registered trademark) disks may have a large amount ofstorage capacity, the storage medium has been generically used in anelectronic apparatus such as a personal computer, and a digital camera.

In such the storage medium, there are memories wherein a driver and aflash memory are integral parts, and wherein a driver is provided with amemory main body or another card-typed memory, for example. At any rate,this storage medium has recently had a considerable amount of storagecapacity.

Such the considerable amount of storage capacity of the storage mediumcauses the driver to generate a great amount of heat, thereby resultingin a malfunction therein.

In order to avoid the malfunction, it is conceivable that a cooler willbe provided with the electronic apparatus side wherein a technologyusing a heat pipe is used as cooling method.

The heat pipe is a metallic pipe having a wick structure on an insidewall thereof, maintained under vacuum, and filled with a small amount ofwater, alternatives for chlorofluorocarbons or the like. An end of theheat pipe is attached to heat source to be heated and a working fluidthen evaporates or is vaporized in the heat pipe, whereby heat isacquired as latent heat (of evaporation). The vapor is moved toward alow-temperature portion thereof rapidly (almost at the velocity ofsound) and it then turns back to a liquid condition by cooling of thelow-temperature portion and extracts heat (liberated heat as latent heatwhen vapor condenses). The working fluid returns to its originalposition through the wick structure (or by gravity) so that heattransfer can be successively performed with efficiency.

Since the conventional heat pipe has a pipe shape and occupies a largespace, it is unsuitable for a cooler for an electronic apparatus such asa personal computer, and a digital camera because the cooler is requiredto be downsized and low-profiled.

In order to downsize the heat pipe, a cooler has proposed such thatsilicon and glass board members each having grooves on their matingsurfaces are connected together to form a passage between them as theheat pipe. Note that as connecting them, the passage is filled with asmall amount of water, alternatives for chlorofluorocarbons or the likeand sealed. Such the liquid changes in phase into and from the vaporinside the heat pipe, thereby serving as the heat pipe.

If, however, the heat pipe is formed using the silicon board member asdescribed above, an object to be cooled diffuses too much heat becauseof high thermal conductivity of silicon itself. This causes inadequateor no evaporation of the working liquid inside the heat pipe, therebyfailing to suitably deliver a performance of the heat pipe.

In order to improve the inconvenience, the inventors have proposed sucha technology that a plastic board member having low thermal conductivitycan be used instead of silicon board member, thereby preventing the heatfrom being improperly diffused at a surface of the board member to allowa performance of the heat pipe to improve.

In this case, however, it is difficult to transfer the heat from anobject to be cooled into the working liquid inside the heat pipe becauseof low thermal conductivity of the plastic material itself, therebyresulting in inadequate evaporation of the working liquid inside theheat pipe. This may fails to suitably deliver a performance of the heatpipe.

DISCLOSURE OF THE INVENTION

The present invention has been contrived in the above circumstances andan object of the present invention is to provide a cooler having anexcellent cooling performance, which is capable of being downsized andlow-profiled, an electronic apparatus and a method for fabricating thecooler.

A cooler according to first aspect of the present invention comprisesfirst board member having a cavity portion formed on a surface thereof,the cavity portion corresponding to a part of a heat pipe excluding atleast a wick part (a structure for allowing capillary action to begenerated) therefrom, second board member having at least a groove forthe wick part formed on a surface thereof, the second board member beingmade from material having higher thermal conductivity than the firstboard member has, the surface of the second board member being adheredto the first board member, and third board member incorporating thesecond board member through a surface thereof, the surface of the thirdboard member being adhered to the first board member.

According to the invention, the first and third board members areadhered to each other. Their surfaces opposed to each other are matchedso that the cavity portion can be served as a passage for heat pipe.This allows the cooler to be downsized and low-profiled. Since the wickpart is made from the material having higher thermal conductivity suchas copper and nickel, thermal transfer can be effectively performed inthis part. Additionally, a condenser part and the wick part areremovable and the condenser part is also made from material havinghigher thermal conductivity such as copper and nickel. This allows acooling performance of the heat pipe to be improved. Since the first andthird board members are made from plastic or glass material, they areavailable for being processed in actuality. They, however, have pooradhesion properties. According to the invention, an adhesive member isprovided between the first and third board members to complement theiradhesion properties. Incidentally, as a combination of the first andthird board members in this case, both members are preferably glass orplastic board members. It is also preferable that one is glass boardmember and the other is plastic board member. Further, as a matter ofcourse, silicon board member is available. If taking a cost performance,a suitable assembly, and the like into account, silicon, copper and thelike may be preferably used as the suitable adhesive.

An electronic apparatus according to second aspect of the inventioncomprises a slot portion into which a card-typed storage medium having aflush memory and a driver is detachably inserted, or a driver providedwith the device side or a driver equipped with a portion separated fromthe device, and a cooler having the above configuration for transferringheat generated from the driver.

In the invention, the above configured cooler having an excellentcooling performance, which is downsized and low-profiled, is equippedwith the electronic apparatus. This prevents the apparatus itself fromsuffering from thermal malfunction.

A method for fabricating a cooler according to third aspect of theinvention comprises the steps of forming first board member having acavity portion on a surface thereof the cavity portion corresponding toa part of a heat pipe excluding at least a wick part therefrom, formingsecond board member having at least a groove for the wick part on asurface thereof, said second board member being made from materialhaving higher thermal conductivity than said first board member has,incorporating the second board member to third board member through asurface thereof, and adhering a surface of the third board member to asurface of the first board member. According to the invention, it ispossible to effectively fabricate the cooler having the aboveconfiguration with reliability.

According to an embodiment of the invention, in the method forfabricating the cooler, the steps of forming fourth board member havingat least a groove for a condenser part on a surface thereof, the forthboard member being made form material having higher thermal conductivitythan the first board member has, and incorporating the forth boardmember to the third board member through a surface thereof are provided.According the embodiment having such the configuration, the condenserpart also has higher thermal conductivity. This allows heat to be muchtransferred.

According to another embodiment of the invention, in the method forfabricating the cooler, the second board member or the fourth boardmember is formed under a process of UV-Lithografie GalvanoformungAbformung (UV-LIGA). According the embodiment having such theconfiguration, it is possible to effectively form a narrow groove.

Finally, according to further embodiment of the invention, in the methodfor fabricating the cooler, a step of forming adhesive members on any ofa surface of the first board member and a surface of the third boardmember to adhere the first and third board members is further provided.This allows an adhesion between the first and third board members withreliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view illustrating a configuration of acooler embodying the invention;

FIG. 2 is a side view illustrating an assembled condition of the coolerembodying the invention;

FIG. 3 is a top plan view showing a lower board member in the coolerembodying the invention;

FIG. 4 is a top plan view showing upper complex board members in thecooler embodying the invention;

FIG. 5 is a top plan view showing an assembled condition of the uppercomplex board members and the lower board member in the cooler embodyingthe invention;

FIG. 6A is a diagram showing an area where heat is diffused as plasticboard member is used;

FIG. 6B is a diagram showing an area where heat is diffused as complexboard members made from plastic material and metallic material are usedaccording to the invention;

FIG. 7 is a flow diagram showing a fabrication method for fabricatingthe cooler of the invention;

FIG. 8A is a schematic diagram illustrating a step for forming a grooveon each of the board members for the condenser and the wick,respectively, used in the cooler of the invention;

FIG. 8B is a schematic diagram illustrating a step for forming a grooveon each of the board members for the condenser and the wick,respectively, used in the cooler of the invention;

FIG. 8C is a schematic diagram illustrating a step for forming a grooveon each of the board members for the condenser and the wick,respectively, used in the cooler of the invention;

FIG. 8D is a schematic diagram illustrating a step for forming a grooveon each of the board members for the condenser and the wick,respectively, used in the cooler of the invention;

FIG. 9 is a schematic diagram illustrating a step for making boardmembers for the condenser and the wick, respectively, incorporated tothe upper board member used in the cooler of the invention;

FIG. 10A is a schematic diagram illustrating a step for adhering theupper complex board member to the lower board member, both members beingused in the cooler of the invention;

FIG. 10B is a schematic diagram illustrating a step for adhering theupper complex board member to the lower board member, both members beingused in the cooler of the invention;

FIG. 11 is a schematic diagram illustrating another cooler embodying theinvention; and

FIG. 12 is a schematic perspective view of a personal computer equippedwith a cooler according to the invention.

BEST MODE FOR CARRYING OUT TH INVENTION

Embodiments of the present invention will be described more in detailwith reference to the drawings.

(Cooler)

FIG. 1 is an exploded perspective view of a cooler embodying theinvention and FIG. 2 is a side view illustrating an assembled conditionof the cooler.

As shown in FIGS. 1 and 2, the cooler 1 comprises four board members 10,20, 30 and 40. Lower board member 10 is made from plastic material andhas a rectangular shape, which is set on a lower location. The boardmember 20 for a condenser part and the board member 40 for a wick partare made from metallic material such as nickel and have a rectangularshape, respectively. The upper board member 30 is made from plasticmaterial and has a rectangular shape, which is set on an upper location.The board member 20 for the condenser part and the board member 40 forthe wick part are inserted into openings 32 and 34 of the upper boardmember 30, respectively, with them being made integral thereto. Thesefour board members 10, 20, 30 and 40 are adhered and fixed through anadhesive member such as silicon member 50. The respective board members10, 20, 30 and 40 have a cavity portion 11, a groove 21, a hollowportion 31 and a groove 41 at their surfaces, 10 a, 20 b, 30 b and 40 b.The cavity portion 11, the groove 21, the hollow portion 31, and thegroove 41 are formed so that they can be served as a looped heat pipe asthese four board members are adhered.

Configurations of the cavity, the grooves, and the hollow formed in theboard members 10, 20, 30 and 40 will be described more in detail withreference to the FIGS. 3 and 4.

As shown in FIG. 3, the lower board member 10 has the cavity portion 11at its surface 10 a This cavity portion 11 has a major empty spacecomprising a portion forming a passage for flowing working liquid and avapor and a portion serving as a storage tank for supplying the workingliquid. With reference to more detailed explanation of the configurationthereof the portion forming the passage 12 for flowing the workingliquid such as water is provided, and the liquid is introduced into theboard member 40 for the wick part, which will be explained, through thepassage 12. The introduced liquid is made evaporated through the boardmember 40 for the wick part and a vapor thus evaporated is thenintroduced into a portion forming a vapor receiver 14. The vapor isintroduced through a portion forming a passage 15 into a condenser part22 for transition from the vapor to liquid, and the condensed liquid isthen moved to a portion forming low temperature part 16. It then returnsto the passage 12. Thus, circulation from liquid to vapor and vice versacan be performed.

A reservoir 13 and a storage portion 17 keep the liquid stored. Theliquid in the reservoir 13 is flowed into the vapor receiver 14 when anamount of liquid in the receiver 14 lowers below a set level. The liquidin the storage portion 17 is flowed into the low temperature part 16when an amount of liquid in the low temperature part 16 lowers below aset level. Thus, the reservoir 13 and the storage portion 17 keep theliquid stored to prevent a space inside the heat pipe from being driedout so that the liquid can be flowed into the reservoir 13 and thestorage portion 17 when necessary.

A heat insulation hall 18 exists at a center of the lower board member10 and at a location adjacent to the passages 12, 15. This prevents theheat from being diffused.

As shown in FIG. 4, the upper board member 30 incorporates the boardmember 20 for the condenser part and the board member 40 for the wickpart, respectively, thereby forming an upper complex board member 100.

The board member 20 for the condenser part has a groove 21 on itssurface 20 b. The groove 21 serves as the condenser part for allowingthe vapor introduced via the passage 15 to be condensed to the liquidand circulates it to the low temperature part 16.

The board member 40 for the wick part has a groove 41 on its surface 40b. The groove 41 serves as the cooler part for allowing the liquidintroduced via the passage 12 and the reservoir 13 to be vaporized andthe vapor thus vaporized to be flowed into the receiver 14.

A heat insulation hall 34 exists at a location opposed to that of theabove heat insulation hall 18. The respective upper and lower boardmembers 10, 30 have the heat insulation halls 18, 34 as a hollow and acavity, for preventing the heat from being diffused.

FIG. 5 shows an adhered condition of the upper complex board member 100and the lower board member 10 through the silicon member 50 as shown inFIG. 2.

The heat pipe formed as the upper complex board member 100 and the lowerboard member 10 are adhered is filled with the working liquid. Thefilled liquid is circulated inside the heat pipe with making a liquid tovapor transition or a vapor to liquid transition. This allows the heatto be transferred, thereby serving as the cooler 1.

The circulation from the liquid to the vapor and vice versa will beexplained with starting at the passage 12 for convenience ofexplanation.

The liquid, first, flows from the passage 12 into the wick part 42. Whenan amount of liquid flowed into the wick part 42 lowers below a setlevel at this time, the reservoir 13 supplies the sufficient liquidthereto to order to avoid drying out the heat pipe.

In the wick part 42, the flowed liquid is heated and boiled. The vaporevaporated according to the boil flows into the reservoir 14. The vaporthen flows through the passage 15 into the condenser part 22 forcondensing it to the liquid. Thus, the condensed liquid flows into thelow temperature portion 16 positioned below the condenser part 22. Theliquid again flows from the low temperature portion 16 to the passage 12to circulate it. When an amount of liquid flowed from the lowtemperature portion 16 to the passage 12 lowers below a set level, thestorage portion 17 allows the stored liquid to flow into the lowtemperature portion 16.

Although the embodiment using the board members made from the plasticmaterial has been explained, the board member made from the glassmaterial or a combination of the plastic material and the glass materialmay be used instead thereof.

Although the embodiment using the board member 20 for the condenser partand the board member 40 for the wick part each made from nickel has beenexplained, cooper can be used for them.

FIGS. 6A and 6B are diagrams for comparing the board member made fromplastic material and the complex board member of the plastic materialand the metallic material according to the invention in terms of theheat diffusion, each schematically showing an area where heat isdiffused for a set time on the board member. FIG. 6A shows an area wherethe heat is diffused as the board member made from plastic material isused. FIG. 6B shows an area where the heat is diffused as the complexboard members made from the plastic material and the metallic materialare used with the plastic board member incorporating the metal such asnickel.

If the board member is made from the plastic material, as shown in FIG.6A, the heat from heat source (the wick part) A-1 diffuses in a littlearea in the directions indicated by arrows (A-2). On the other hands, ifthe complex board member made from the plastic material and the metallicmaterial is used as shown in FIG. 6B, the heat from heat source (thewick part) B-1 highly diffuses in a metallic portion but little heatdiffuse in the plastic portion around the metallic portion (B-2).

The wick part is required for having thermal conductivity higher than aset level in order to serve as the heat pipe. Since the board membermade from the plastic material, as shown in FIG. 6A, has littleconductivity, it does not sufficiently serve as the heat pipe. On theother hands, in the complex board member made from the plastic materialand the metallic material, as shown in FIG. 6B, according to theinvention, the heat is sufficiently tansferred in the wick part but itis hard to diffuse in the plastic portion around the wick part. Thismeans that the heat concentrates in the wick part, thereby sufficientlyserving as the heat pipe.

(A Method for Fabricating the Cooler)

FIG. 7 shows a fabrication method for fabricating the cooler.

The lower board member 10 and the upper board member 30 are first formedso that the cavity and hollow portions can be served as the heat pipe(Step 701). The cavity portion 11 working as a passage, a storage tankfor storing working liquid, and a heat insulation hall is formed on thesurface 10 a of the lower board member 10 made from the plasticmaterial. The hollow portion 31 working as a heat insulation hall isformed on the surface 30 b of the upper board member 30 made from theplastic material. As the method for forming these cavity and hollowportions, it is conceivable that a mould for each of the board membersis previously made, and the board members may be shaped into aparticular form using the mold. The upper and lower board members may bemade from glass. If so, the cavity and hollow portions may be etchedinto a piece of glass after patterning thereof.

Next, the board member 20 for the condenser part and the board member 40for the wick part are formed (Step 702). Each of the board members 20,40 that have grooves is formed according to the so-called UV-LIGA, forexample.

Detailed steps of the UV-LIGA will be explained with reference to FIGS.8A through 8D.

Photoresist layer 81 made from organic material such as SU-8 is firstformed on a plate 82 and patterned photoresist film 83 is then formed onthe layer 81, as shown in FIG. 8A. They are referred to as a patternboard 80.

The photoresist layer 81 is then etched applying ultraviolet light UVtoward the pattern board 80 from above, as shown in FIG. 8B.

Further, as shown in FIG. 8C, the photoresist film 83 is removed fromthe pattern board 80 and nickel layer 84 is then formed on a surfacethereof by electroforming of nickel Ni.

Next, as shown in FIG. 8D, the nickel layer 84 is removed from thepattern board 80. Accordingly, the nickel layer thus removed becomesavailable for the board member 20 for the condenser part and the boardmember 40 for the wick part, which have grooves.

The board members 20, 40 thus formed are inserted into the openings 32,34 opened through the upper board member 30 as shown in FIG. 9 (Step703). When the upper board member 30 made from plastic material isheated resulting in semi-solid condition, the board member 20 for thecondenser part and the board member 40 for the wick part are insertedinto the openings 32, 34 of the upper board member 30 thus heated tomake the board members 20, 30, and 40 integral without a crack.

Additionally, as shown in FIG. 10A, a copper thin film 10 b as anadhesive member is formed on the surface 10 a of the lower board member10 using, for example, the spattering. The lower board member 10 and theupper complex board member 100 are then bonded to each other using, forexample, an ultrasonic bonding or a heat fusion bonding (Step 704).

The above method allows the heat pipe to be effectively fabricated.

(Another Embodiment of Cooler)

FIG. 11 illustrates a flexible cooler 120 comprising a board device 122for a condenser part, a board device 124 for wick part, and a flexibleboard member 121 connecting the board devices 122 and 124.

The board device 122 for the condenser part and the board device 124 forwick part are respectively made from plastic materials, into which theboard member 20 for the condenser part and the board member 40 for thewick part are respectively inserted according to the above method.

The flexible board member 121 is made from plastic material and includesa passage 123 for heat pipe. The heat pipe is formed with these boardmember and devices being made integral.

The flexible board member 121 is made flexible without restraint. It isillustratively capable of equipping its board member 124 for the wickpart for a heat source portion of an electronic apparatus and closelyconnecting the flexible board member along an outer surface of theelectronic apparatus.

According to the cooler having such the configuration, the heat pipe maybe effectively equipped even when the space therefor is limited, therebyallowing the electronic apparatus to be downsized and low-profiled.

(Electronic Apparatus)

FIG. 12 is a schematic perspective view of a personal computer equippedwith a cooler according to the invention.

The personal computer 130 has a slot 131 for inserting and withdrawingstorage medium 134 having a flush memory 133 and a driver 132. Thecooler 135 of the invention is placed in the personal computer 130 withits wick part being illustratively situated directly under the driver132 as the storage medium 134 is inserted into the personal computerthrough the slot 131.

Although the electronic apparatus has been explained as the personalcomputer, the cooler according to the invention may be used for otherelectronic apparatus such as digital cameras and video cameras.

(Others)

Although it has been explained according to the above embodiments of theinvention that the upper board member 30 and the lower board member 10are made from plastic or glass material and the board members 20, 40 forthe condenser part and the wick part are made from metallic material,this invention is not limited thereto. The invention has such a featurethat each of the board members 20, 40 has a grater (higher) thermalconductivity than the upper and lower board members 10, 30 have.

The following table 1 illustratively indicates materials suitablyapplied for the board members 20, 40 for the condenser part and the wickpart and their thermal conductivity. The following table 2illustratively indicates materials suitably applied for the upper andlower board members 10, 30 and their thermal conductivity. TABLE 1THERMAL CONDUCTIVITY MATERIALS (k/Wm⁻¹K⁻¹) Silicon 168 Aluminum 240Copper 395 Nickel 83 Iron 72 Titanium 17 Special Plastic 100

TABLE 2 THERMAL CONDUCTIVITY MATERIALS (k/Wm⁻¹K⁻¹) Pyrex Glass About 1Plastic About 1

Further, special plastic having more than 100 times the thermalconductivity of conventional plastic has been recently developed bymixing good thermal conductive ceramic powder and low temperaturesoluble alloy powder with granular plastic raw material, heating andmolding them. Thus, it is conceivable that, if such the special plasticis used for materials for the board members for the condenser part andthe wick part, and plastic or glass having a normal thermal conductivitysuch as Pyrex (registered trademark) glass is used for materials for theupper and lower board members, the board members for the condenser partand the wick part have grater thermal conductivity than the upper andlower board members have.

Note that, if plastic or glass having a normal thermal conductivity suchas Pyrex glass is used for materials for the upper and lower boardmembers, the board members for the condenser part and the wick part mayhave more than 10 times the thermal conductivity of the upper and lowerboard members when the board members for the condenser part and the wickpart are made from titanium.

Similarly, if the board members for the condenser part and the wick partare made from iron or nickel, they may have more than 50 times thethermal conductivity of upper and lower board members. Additionally, ifthe board members for the condenser part and the wick part are made fromthe above special plastic, aluminum or silicon, they may have more than50 times the thermal conductivity of upper and lower board members.Further, if the board members for the condenser part and the wick partare made from copper, they may have more than 300 times the thermalconductivity of upper and lower board members.

As described above, according to the invention, it is possible toprovide the cooler having an excellent cooling performance, which iscapable of being downsized and low-profiled, an electronic apparatus,and a method for fabricating the cooler.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful when it isapplicable to a compact cooler for cooling card-typed storage medium.The present invention is also useful when it is applicable to a compactelectronic apparatus such as note-typed personal computer, and digitalcameras, which include the card-typed storage medium. The presentinvention is further useful when it is applicable to a method forfabricating a compact cooler for cooling card-typed storage medium

1-7. (canceled)
 9. A method for fabricating a cooler comprising thesteps of: forming first board member having a cavity portion on asurface thereof, said cavity corresponding to a part of a heat pipeexcluding at least a wick part therefrom; forming second board memberhaving at least a groove for the wick part on a surface thereof, saidsecond board member being made from material having higher thermalconductivity than said first board member has; incorporating said secondboard member to third board member through a surface thereof; andadhering a surface of the third board member to a surface of the firstboard member.
 10. The method according to claim 9 further comprising thesteps of: forming fourth board member having at least a groove for acondenser part on a surface thereof, said forth board member being madeform material having higher thermal conductivity than said first boardmember has; and incorporating said forth board member to said thirdboard member through a surface thereof.
 11. The method according toclaim 9, wherein said second board member is formed under a process ofUV-LIGA:
 12. The method according to claim 9 further comprising a stepof forming adhesive members on any of the surfaces of said first andthird board members to adhere said first and third board members.